The splitting of the fundamental modes in a microcavity requires a strong coupling between light and matter and plays a significant role in quantum technology. A linear dynamic magnetoactive fluid cavity supporting ultrasonic waves is designed to enhance wave-matter interaction and induce splitting of resonant cavity-acoustic modes due to magneto-thermal and photothermal effects. The magneto-caloric force due to a temperature gradient within the cavity was used to realize a self-driven fluid cavity without an external mechanical pump. This force can be modulated remotely by a DC magnetic field or laser-induced surface-temperature change of the fluid within the cavity. An ultrasonic wave propagating through this cavity with moving fluid can be influenced by Doppler shift and rheological modifications leading to acoustic Zeeman-like splitting induced by external optical irradiation in the presence of a magnetic field. The laser-induced control of the fluid flow within the cavity enables the frequency and amplitude modulation of broadband ultrasonic waves traveling through the cavity leading to the nonreciprocal transmission of acoustic waves.
Time-entanglement is a promising resource for the implementation of quantum communications over standard fiber networks. In particular, photonic qudits can enhance the performance of quantum communication, including quantum key distribution, in terms of noise robustness, quantum information content, distance reach, as well as security and secret key rates. However, time-entangled photonic qudits are not ready yet to be fully exploited for quantum communications in fiber networks that are fully compatible with standard telecommunication architecture. Here, we demonstrate the implementation of telecommunication-compatible quantum communications based on picosecond-spaced time-entangled qudits. To this end, we make use of an integrated photonic chip comprising a cascade of programmable interferometers and a spiral waveguide. We use entangled qudits to implement high-speed quantum key distribution, chip-to-chip entanglement distribution, and quantum state propagation over 60 km of standard fiber. Our results show the potential of time-entangled qudits for high-speed quantum communications in telecommunication-compatible architecture.
Because of their safety, environmental friendliness, and simple operation, light-driven films are widely used in the fields of environment, biomedicine, and micromechanics. For light-driven films, moving the film on the liquid surface via the Marangoni effect is a convenient, mainstream approach. The efficient photothermal conversion can generate thermal Marangoni flow rapidly, and the superhydrophobicity can reduce the drag when the light-driven film moves on the liquid surface. In this work, a new strategy for preparing the composite film with excellent photothermal and superhydrophobic properties is proposed. The fSiO2/MG-WPU(fluoroalkylsilanes-SiO2/MXene@gold-waterborne polyurethane) film was obtained by simple spraying. The localized surface plasmon resonance effect improved the light absorption of MG(MXene@gold) hybrid, which is beneficial to the photothermal conversion. The absorption of the fSiO2/MA-WPU film reached 84% in the wavelength band from 300 to 1400 nm. The prepared MXene composite films show superhydrophobic property. The contact angle and sliding angle of the composite film reached to 154° and 2.3°, respectively. The film has good photothermal conversion ability, and its temperature reached 121 °C within 300 s (808 nm laser, 0.5 W/cm2). Combining high photothermal conversion and superhydrophobicity, the fSiO2/MG-WPU composite film achieved excellent performance for light driving. When irradiating with a laser power of 2 W/cm2, the film linearly advanced 12.8 cm in 12 s. Furthermore, the film completed the actions such as clockwise rotation and counterclockwise rotation. The multifunctional fSiO2/MG-WPU composite film provides a new platform for remote control devices, light-driven micro-robots, reagent micro-transporters, etc.
To achieve quantum computing on chip, the chip-scale photonic quantum technologies indispensably request efficiently coupling and guiding spontaneous emission from solid-state quantum emitters (QEs) as central blocks for high-quality single-photon sources. Here, we experimentally demonstrate a deterministically positioned nano-diamond (ND) as QE which is manipulated on chip via Archimedean spiral gratings to spontaneously trigger single photons carrying spin and orbital angular momentum superposition states.
We review our work on implementing integrated QFC sources based on microring resonators for on-chip generation of two- and multi-photon time-bin entangled states, d-level frequency-entangled photon pairs, and multipartite d-level cluster states. We also present our recent progress on telecom-compatible, scalable, time-entangled two-photon qubits using on-chip Mach-Zehnder interferometers (MZI) in combination with spiral waveguides. Both approaches are highly cost-effective, efficient, and practical, since we coherently manipulate the time and frequency modes through standard fiber-linked components that are compatible with off-the-shelf telecommunications infrastructures. Our work paves the way for robust sources and processors of complex photon states for future quantum technologies.
In modern medicine, wound healing remains a very complex process where the main goal is to achieve a fast regeneration matched to an aesthetically satisfactory appearance. In particular, reducing the wound healing time and minimizing tissue scarring are important requirements. In view of minimally-invasive clinical interventions, nanoparticle-assisted laser tissue soldering is emerging as an appealing concept in surgical medicine due to its ability to facilitate wound healing while avoiding sutures. However, such a therapy has not been employed in clinical settings yet. The underlying reason is the fact that rapid elevation in temperature can cause significant photothermal tissue damage. Therefore, cutting-edge diagnostic tools are indispensable in order to monitor the temperature in tissue and achieve satisfactory healing results. To this end, we propose a non-invasive, non-contact, and non-ionizing modality for monitoring nanoparticle-assisted laser-tissue interaction and visualizing the localized photothermal damage, by taking advantage of the unique sensitivity of terahertz radiation to the hydration level of biological tissue. We demonstrate that terahertz imaging can be employed as a versatile tool to monitor the temperature variations and reveal the thermally affected evolution in tissue. In particular, terahertz imaging is able to provide quantitative information along the depth direction, in turn allowing us to characterize the photothermal damage induced by nanoparticle-assisted laser tissue soldering in three dimensions. Our approach can be easily extended and applied across a broad range of clinical applications associated with laser-tissue interactions, such as laser ablation and photothermal therapies.
Linearly polarized quantum sources with high purity and well-defined polarization angles are the fundamental blocks in the photonic quantum technological evolution. However, due to the orientation of the dipole moment with the quantum emitters, the polarization state of the emitted photons is intrinsically limited. Therefore, it is impossible to generate arbitrary linear polarization states simultaneously. Here, we propose a new concept of versatilely generating linearly polarized emission based on a quantum metasurface platform that combines nano-diamonds containing color centers with metasurface-decorated waveguides. By tailoring the size and orientation of the slit meta-atom on the waveguide, linearly polarized emission with arbitrary polarization angles can be achieved with the degree of linear polarization larger than 0.999.
Absorption of light is critical to light-trapping devices such as photovoltaics, biosensors, photodetectors, etc. Naturally occurring materials have weak absorption, while perfect absorbers based on metamaterials are developed to solve the weak light absorption of light-harvesting devices. This presentation will provide an overview of metamaterial absorber enhanced light harvesting devices and our recent research progress on metamaterial absorbers.
Transmission properties of transverse magnetic light through periodic sub-wavelength slit apertures on a metallic film, behind which is another planar metallic film, are studied by finite-difference-time-domain method with constant periodicity and slit width. The result shows that the transmitted energy is strongly correlated to both the thickness of the metallic grating and the distance between such two films at a specific wavelength. The thickness of the grating acts as a filter that allows specific wavelengths to go through the slits, while the distance of dual metallic film dominantly determines a constructive or destructive interference between the transmitted light through the slits and the reflected wave from the back film. Besides, a strong vibration in the transmission spectrum as a function of the grating thickness is interestingly observed, which can be interpreted by the resonance of the surface plasmons of the front and the back metallic films.
Optical square wave sources are particularly important for applications in high speed signal processing and optical communications. In most realizations, optical square waves are generated by electro-optic modulation, dispersion engineering of mode-locked lasers, polarization switching, or by exploiting optical bi-stability and/or optical delayed feedback in semiconductor diode lasers, as well as vertical-cavity surface-emitting lasers (VCSELs). All such configurations are bulky and cause significant timing jitters. Here we demonstrate the direct generation of optical square waves from a polarization-maintaining figure-eight nonlinear amplifying loop mirror (NALM) configuration that uses an embedded high index glass micro-cavity as the nonlinear element. Such a NALM mimics the behavior of a saturable absorber and has been used to reach passive mode-locking of pico- and even nano-second pulses. In our method, the NALM, including a high-Q micro-ring resonator, acts as an ultra-narrowband spectral filter and at the same time provides a large nonlinear phase-shift. Previously we have demonstrated that such a configuration enables sufficient nonlinear phase-shifts for low-power narrow-bandwidth (~100 MHz FWHM) passive mode-locked laser operation. Here we demonstrate the switching of stable optical square wave pulses from conventional mode-locked pulses by adjusting the cavity properties. In addition, the square wave signal characteristics, such as repetition rate and pulse duration, can be also modified in a similar fashion. The source typically produces nanosecond optical square wave pulses with a repetition rate of ~ 120 MHz at 1550nm. In order to verify the reach of our approach, we compare our experimental results with numerical simulations using a delay differential equation model tailored for a figure-eight laser.
InGaAsP/InP-air-aperture micropillar cavities are proposed to serve as 1.55-μm single photon sources, which are indispensable in silica-fiber based quantum information processing. Owing to air-apertures introduced to InP layers, and adiabatically tapered distributed Bragg-reflector structures used in the central cavity layers, the pillar diameters can be less than 1 μm, achieving mode volume as small as ~(λ/n)3, and the quality factors are more than 104 - 105, sufficient to increase the quantum dot emission rate for 100 times and create strong coupling between the optical mode and the 1.55- μm InAs/InP quantum dot emitter. The mode wavelengths and quality factors are found weakly changing with the cavity size and the deviation from the ideal shape, indicating the robustness against the imperfection of the fabrication technique. The fabrication, simply epitaxial growth, dry and chemical etching, is a damage-free and monolithic process, which is advantageous over previous hybrid cavities. The above properties satisfy the requirements of efficient, photonindistinguishable and coherent 1.55-μm quantum dot single photon sources, so the proposed InGaAsP/InP-air-aperture micropillar cavities are prospective candidates for quantum information devices at telecommunication band.
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